From: Jeff King <peff@peff.net>
To: Farhan Khan <khanzf@gmail.com>
Cc: git@vger.kernel.org
Subject: Re: pack file object size question
Date: Mon, 17 Dec 2018 14:39:50 -0500 [thread overview]
Message-ID: <20181217193949.GC9853@sigill.intra.peff.net> (raw)
In-Reply-To: <CAFd4kYCHefqRsiFK=K7MHp=MTwOBXB5979WobEm3w1J5q1bZ0w@mail.gmail.com>
On Sun, Dec 16, 2018 at 04:52:13PM -0500, Farhan Khan wrote:
> It seems that there is a 12 byte header (signature, version, number of
> objects), then it immediately jumps into each individual object. The
> object consists of the object header, then the zlib deflated object,
> followed by a SHA1 of the above. Is this accurate?
Others discussed the length confusion, but I wanted to point out one
more thing: the packfile does not contain the sha1 of each object. That
is computed by index-pack (but there is a sha1 of the contents of the
_entire_ packfile).
A bit error on the wire will be detected by the whole-pack sha1. A bit
error on the sender's disk generally be detected by zlib, but not
always. The ultimate check that the receiver does is make sure it has
all of the expected objects by walking the object graph from the
proposed ref updates. Any object which has an undetected bit error will
appear to be be missing (as well as any object that the sender actually
just failed to send).
-Peff
prev parent reply other threads:[~2018-12-17 19:39 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-16 21:52 pack file object size question Farhan Khan
2018-12-16 22:14 ` Jonathan Nieder
2018-12-16 23:36 ` Farhan Khan
2018-12-17 0:14 ` Jonathan Nieder
2018-12-17 15:31 ` Duy Nguyen
2018-12-17 19:39 ` Jeff King [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
List information: http://vger.kernel.org/majordomo-info.html
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20181217193949.GC9853@sigill.intra.peff.net \
--to=peff@peff.net \
--cc=git@vger.kernel.org \
--cc=khanzf@gmail.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
Code repositories for project(s) associated with this public inbox
https://80x24.org/mirrors/git.git
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).